Mobile communication systems were developed to provide the subscribers with voice communication services on the move. With the rapid advance of technologies, the mobile communication systems have evolved to support high speed data communication services beyond the early voice-oriented services. However, the limited resource and user requirements for higher speed services in the current mobile communication system spur the evolution to more advanced mobile communication systems.
In order to meet such requirements, Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are under the standardization by the 3rd Generation Partnership Project (3GPP) as one of the next generation mobile communication systems. LTE is a technology for realizing high-speed packet-based communications with the data rate of up to 100 Mbps. In order to accomplish this, a discussion is being held on several schemes: one scheme for reducing the number of nodes located in a communication path by simplifying a configuration of the network, and another scheme for maximally approximating wireless protocols to wireless channels.
Recently, with the introduction of LTE to the hot spot area, various wireless communication networks such as LTE, Global System for Mobile communications (GSM), and Universal Mobile Telecommunications System (UMTS) coexist in the same area. Accordingly, the terminal is configured to support multiple Radio Access Technologies (RATs) including GSM and UMTS as well as LTE radio. Also, the networks are operating in the multi-RAT environment such that the terminal operates in such a way of selecting one of multiple RATs.
However, if an error occurs at the control node managing some RATs or if the system reboot occurs with the necessity of system upgrade, the terminals operating with the corresponding RAT select different RATs simultaneously so as to cause overload to the system temporarily.
There is therefore a need of a method for controlling the system overload which may occur in the above situation.